Unplug the Dremel power cord from the outlet. Place the Dremel on a flat work surface. Look for the small round seam with a small slot near the rear of the tool. This is the brush cap. There either will be one on each side of the unit or on the top and bottom depending on your model.
Turn the round brush caps counterclockwise with the screwdriver end of the Dremel tool and remove them from the Dremel. If you do not have the Dremel tool, use a jeweler's flat-head screwdriver.
Grasp the springs inside the housing, located on each side, with your fingers and pull them out. The brushes are on the end of the springs. Each brush is a square armature that is curved on one end and has a small round pin connecting to the spring on the other end. Pull the brushes of the end of the spring.
Install new brushes onto the end of each spring. The end of the spring goes around the small round pin on the armature. The curved portion of the brush must point away from the spring.
Insert the brush end into the Dremel, lining up the curved portion with the curve in the housing. Place the brush caps into the holes and turn them clockwise to secure.
Plug the Dremel power cord into a wall socket and operate it for five minutes without a load to help seat the brushes inside the unit.